1. Field of the Invention
This invention relates to a ball which may be used for playing ball games, such as baseball, or may be used as a practice ball for such games.
2. Description of the Prior Art
In baseball, a pitcher will, in order to deceive a batter throw a baseball so that it describes curves which differ from the normal or expected trajectory from the mound to the plate. Only pitchers with the appropriate level of skill can produce effective pitches of this general type, variants of which are termed `curve`, `slider`, `sinker` and `break`.
It is known that such trajectories can be obtained or exaggerated by tampering with the ball. This is discussed in an article entitled `Masters of Mischief` which appears on pages 92 and 93 of the October issue of `Science `83`. The theory behind the behaviour of baseballs when pitched to curve to the plate is not well understood, although it appears that atmospheric conditions can affect the degree of curve.
In U.S. Pat. Nos. 4,128,238 and 4,286,783, both to Newcomb and Newcomb, Jr., there are described practice baseballs which have portions of the surface removed to allow the ball to curve when it is pitched as a straight ball. As the ball is not generally spherical, it cannot properly be used for playing baseball, but may only be used as a practice ball.
The behaviour of the ball in the game of cricket can be similar to the described movement of a baseball. In cricket, the ball can be made to `move` or `swing` by a skilled bowler, the movement being to the left or to the right of a line from the bowler to the batsman. Of course, in cricket the intention is for the ball to strike the ground before it reaches the batsman, and accordingly the swing or movement takes place before the ball strikes the ground.
In cricket, the movement is believed to be accentuated by polishing one hemisphere of the ball, to one side of the circumferential seam, whilst leaving the other hemisphere unpolished, but again the theory behind the behaviour of the ball is not well understood. United Kingdom Patent application No. 2091110A to Phillips describes a simulated cricket ball which assists an inexperienced bowler in obtaining `swing`. This is achieved by providing a simulated seam which is higher than that of a conventional ball.
In the design of golf ball surface textures, the only consideration is to produce a ball which will not deviate from an expected trajectory. Thus, the conventional golf ball has a regular pattern of dimples in its spherical surface, the total area of the dimples usually constituting between 55% and 61% of the total surface area of a golf ball.
On page 15 of `Capital City Federal Home Owner`, July-August 1972, published by Capital City Federal Savings & Loan Association of Washington, D.C., there is a brief discussion of the need for such a regular pattern of dimples in an article entitled `Why a golf ball has dimples`.
The article describes empirical flight tests of conventionally dimpled golf balls, golf balls with completely smooth surfaces, and golf balls with one smooth half and one fully dimpled half. Although the article states that the `half-smooth` balls travelled much less further than conventional balls, and that they executed `violent right curve` slices when projected with the dimpled half on the right, and a hook to the left with the dimpled half on the left, no details of the degree of deviation are provided. Furthermore, the aerodynamic behavior of gold balls struck with a high degree of velocity and backspin may not relate to the likely behavior of a much larger hand projected play ball having low velocity and degree of backspin.
None of the prior art balls provides a ball which can be played with as a normal ball, but which can be projected to deviate from a normal or expected path, in games, or to give practice to a hitter or batsman.